Impact of chest wall motion caused by respiration in adjuvant radiotherapy for postoperative breast cancer patients
© Lowanichkiattikul et al. 2016
Received: 7 December 2015
Accepted: 15 February 2016
Published: 24 February 2016
To determine the chest wall movement of each patient during deep inspiratory breath hold (DIBH) and expiratory breath hold (EBH) in postoperative breast cancer patients. Postoperative breast cancer patients who underwent CT simulation for 3D radiotherapy treatment planning during December 2012 to November 2013 were included. Before scanning the radio-opaque wire was placed on the surface for breast and chest wall visualization on CT images, then the patient underwent three phases of CT scanning (free breathing, DIBH, and EBH, respectively). The distances of chest wall motion at five reference points were calculated using the treatment planning system. 38 breast cancer patients who underwent surgery were included. Median age was 48.5 (28–85) years. Median BMI was 23.4 (16.6–38.3) kg/m2. Median lung volume was 3160.5 (1830.8–4754.0) cm3. Median Haller index was 2.43 (1.92–3.56). Median chest wall movement was wider in anteroposterior (A–P, 4.2–5.4 mm) than superoinferior (S–I, 2.5–2.6 mm) and mediolateral (M–L, 0.6–1.1 mm) dimension in all five measured points. There was no significant effect of the type of surgery, BMI, lung volume, and the Haller index on the distances of chest wall movement. Additional margins of 7, 5, and 2 mm to the A–P, S–I, and M–L dimension should adequately cover the extreme chest wall movement in 95 % of the patients. This study showed that the maximal movement of the chest wall during DIBH and EBH was greatest in the A–P axis followed by the S–I axis, while the M–L axis was minimally affected by respiration.
KeywordsBreast cancer Adjuvant radiotherapy Respiration Chest wall motion
Breast cancer is the most common cancer in women (Attasara and Buasom 2011; Siegel et al. 2012). It is known that postoperative breast irradiation can improve local control in early-stage breast cancer (Fisher et al. 2002). According to the anatomy of the breast that lies on the anterior chest wall, intra-fraction movement of the clinical target volume (CTV) can occur due to respiration during treatment delivery. Large treatment margins added to cover the movement may subsequently cause a substantial volume of normal tissue exposed to radiation resulting in increased risk of treatment-related toxicity (Korreman et al. 2006).
It has been assumed that breast motion from breathing during standard whole breast RT does not significantly affect the dose distribution within the breast tissue. In one study the baseline average movement during normal breathing was <2 mm in all dimensions (Chopra et al. 2006). However, in the extreme phase of respiration like DIBH the distance of chest wall movement can be increased up to about 12.6 mm (Pedersen et al. 2004) According to the European Organization for Research and Treatment of Cancer (EORTC) survey of clinical practice in Europe, there was still variation in an additional treatment margin with the mean value of around 7.5 mm (Hans and Coen 2013).
Lung vital capacity has been shown to strongly correlate with the chest wall movement (Cala et al. 1996). Chest wall deformity also affects the chest wall motion in patients with pectus excavatum, with the motion decreasing markedly at the level of deformity (Redlinger et al. 2011). The severity of deformity could be graded by Haller index, which was the ratio of the chest wall width and depth. Increasing Haller index indicated more severe deformity.
This study was planned to evaluate the movement distances of breast or chest wall during DIBH and EBH and also to evaluate factors affecting chest wall movement during respiration.
Consecutive postoperative breast cancer patients, planned for CT simulation for adjuvant radiotherapy in Ramathibodi Hospital from December 2012 to November 2013, were included in the study. Prospective data collection was performed. All patients provided written informed consent, and the study was approved by the institutional ethics committee and funded by the Faculty of Medicine, Ramathibodi Hospital, Mahidol University.
Details of the imaging protocol
Table speed (mm/s)
Slice thickness (mm)
Measurement of chest wall movement
Data was collected using the Eclipse® planning system (Varian Medical Systems, Inc, California, USA). The translational movement of the reference points (S, I, M, L, and A) was recorded in all three dimensions, namely S–I, A–P, and M–L. The maximal movement in each direction of the reference points was calculated from the differences between the markers position during DIBH and EBH. Also the movement of the reference points during DIBH and EBH was compared to the FB position.
Factors affecting chest wall movement
Four factors were explored to find the correlation with chest wall movement including the surgical procedure (mastectomy vs BCS), the body mass index (BMI), the total lung volume during DIBH (lung volumeDIBH) and the Haller index.
Instead of the lung vital capacity, this study aimed to explore the correlation between chest wall movement and the total bilateral lung volume during DIBH. The volume was estimated using auto-contouring tools of the Eclipse® planning system.
The Haller index was used to grade the severity of chest wall deformity and was the ratio of the maximal width of chest wall divided by the minimal distance between the posterior sternum and anterior vertebral body at the same level. In this study, the index was measured in DIBH images (Redlinger et al. 2011).
Statistical data analysis
Mean, standard deviation (SD), median and range of the translational movement in each axis for each reference point was calculated. Spearman’s rank correlation coefficient was used to describe the correlation between BMI, lung volumeDIBH, Haller index and the chest wall movement. Mann–Whitney U test was used to compare the difference of chest wall movement between the mastectomy and BCS group.
Lung volume (cm3)
Chest wall movement
The maximal chest wall movement
95 % coverage
Point of intersection: superior (mm)
3.3 ± 2.8
1.5 ± 1.5
5.7 ± 4.3
Point of intersection: inferior (mm)
3.0 ± 2.9
1.5 ± 1.5
5.8 ± 4.0
Point of intersection: medial (mm)
3.9 ± 3.4
0.8 ± 0.7
5.3 ± 3.8
Point of intersection: lateral (mm)
3.0 ± 3.2
1.2 ± 1.4
4.5 ± 3.2
Point of intersection: anterior (mm)
3.6 ± 2.6
1.3 ± 1.4
5.7 ± 4.2
Distance of chest wall movement during DIBH and EBH comparing to the FB scan
Median distances (mm)
A (−) P (+)
I (−) S (+)
M (−) L (+)
(−21.3 to 0.4)
(−14.2 to 6.4)
(−2.5 to 10.0)
(−5.0 to 10.0)
(−2.5 to 8.5)
(−4.9 to 7.3)
(−21.2 to 1.5)
(−17.1 to 5.8)
(−2.5 to 10.0)
(−5.0 to 12.5)
(−19.3 to 3.2)
(−19.9 to 3.8)
(−15.4 to 0.0)
(−14.5 to 7.8)
(−12.5 to 12.5)
(−12.5 to 12.5)
(−3.5 to 1.8)
(−5.3 to 2.4)
(−11.7 to 3.3)
(−15.7 to 4.4)
(−12.5 to 25)
(−12.5 to 30.0)
(−5.8 to 3.8)
(−9.4 to 4.0)
(−16.5 to 0.8)
(−16.4 to 8.9)
(−2.5 to 12.5)
(−5.0 to 12.5)
(−9.6 to 6.2)
(−10.2 to 5.2)
Factors affecting chest wall movement
Different surgical procedure of the breast affected the shape of the chest wall, however this study showed no statistical significant differences in chest wall movement after mastectomy or BCS, except movement in S–I axis of the lateral marker, which showed more superior movement in BCS as 2.5 mm compared with 0.0 mm (p = 0.041).
For the other factors, data were analyzed to find the correlation between chest wall movement in each axis with BMI, lung volumeDIBH and Haller index (HI). BMI and Haller index both showed no significant correlation with the chest wall movement. Comparing between normal BMI and obese patients, although the distances of chest wall movement in A–P direction of the patients with normal BMI were greater than in obese patients (4.7–6.5 mm compared to 2.6–4.3 mm), the differences were not statistically significant. Movement in the other directions was almost the same in both groups of patients.
There was weak to moderate correlation between lung volumeDIBH and chest wall movement of only some measured points. In S–I axis, only I marker show significant moderate correlation with rs = 0.405. In A–P axis, I, L, and A marker had rs = 0.390, 0.486 and 0.361, respectively. When lung volumeDIBH was categorized into two groups, the patients with larger lung volumeDIBH seemed to have more chest wall movement in A–P direction, 5.4–6.7 mm compared to 2.2–4.6 mm in patients with lung volume ≤3000 cc. However, there were no statistical significant differences between the two groups in all other directions of chest wall movement.
Chest wall motion reported in different studies
Pedersen et al. (2004)
Chopra et al. (2006)
Kinoshita et al. (2008)
1.3 ± 0.5
1.0 ± 0.6
2.6 ± 1.4
Richter et al. (2009)
Wang et al. (2013)
1.38 ± 0.85
1.03 ± 0.48
0.95 ± 0.36
One reason that might explain why there was no strong correlation between different factors and the chest wall movement in this study was the relatively small number of patients with quite homogeneous baseline characteristics. Most patients were not obese with the BMI of 23.4 kg/m2 and there was only one patient with the pectus excavatum. There seemed to be some relationship between the larger lung volumeDIBH and the more movement of the inferior, lateral, and the anterior measured points, which in some part might be explained by the more lung volume change in the lower lung region caused by the diaphragm reflecting in different movement of different part of the chest wall.
Naturally the chest wall moves unevenly during respiration, so applying the uniform margin for all directions in chest wall irradiation might result in over treating the normal tissue or under coverage of the CTV. Considering the distances of movement measured in different phases of breathing in this study the additional margins of 7, 5, and 2 mm to the A–P, S–I, and M–L dimension should adequately cover the extreme chest wall movement in 95 % of the patients. Nevertheless, for clinical practice, margin adding should be individualized as much as possible. Also adding additional margins for setup error might be different from institute to institute.
This study show the maximal movement of the chest wall is in the anterior–posterior axis with is about 5.5–7.18 mm to coverage 95 % of the patients so additional margin of >7.1 mm especially in anterior–posterior axis is required to ensure the clinical target volume coverage from data of this study. But this study does not account for the error in interfraction patients’ setup. So, the additional setup margin should be considered in each setting.
CL designed study, data collections, statistical analysis and drafted the manuscript. MD participated in the design of the study and revised the manuscript. CS participated in the design of the study. SK carried out the treatment planning. PK helped to design the computed tomography protocol. All authors read and approved the final manuscript.
This study was funded by Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Thailand.
The authors declare that they have no competing interests.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
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